Struct EncodingGuard 

pub struct EncodingGuard { /* private fields */ }

Encoding guard to detect potentially malicious encodings.

When block_base64 is enabled and a decoded_content_matcher is provided, the guard will decode base64 candidates and run the decoded text through the matcher to detect threats hidden inside encoded payloads (F-002).

Security features:

• Detects both padded and unpadded base64 candidates
• Recursive decoding up to max_decode_depth layers to catch multi-encoded payloads
• Configurable minimum candidate length (default: 8 chars)
• Supports both STANDARD and URL_SAFE base64 alphabets

Implementations

impl EncodingGuard

pub fn new(name: impl Into<String>) -> Self

Create a new encoding guard

pub fn block_unicode_escapes(self, block: bool) -> Self

Set whether to block unicode escapes

pub fn block_base64(self, block: bool) -> Self

Set whether to block base64

pub fn with_action(self, action: GuardAction) -> Self

Set the action

pub fn with_decoded_content_matcher(self, matcher: PatternMatcher) -> Self

Set a pattern matcher to run against decoded base64 content.

When base64-encoded text is detected and this matcher is set, the guard will decode the payload and check it for threats, catching attacks that hide prompt injections or jailbreaks inside base64 encoding.

pub fn with_max_decode_depth(self, depth: usize) -> Self

Set the maximum recursive decode depth (default: 3).

Attackers may nest base64 encoding multiple times to evade detection. This controls how many layers of encoding the guard will unwrap.

pub fn with_min_candidate_len(self, len: usize) -> Self

Set the minimum candidate length in chars (default: 8).

Strings shorter than this are not considered base64 candidates. Lower values catch shorter payloads but may increase false positives.

Trait Implementations

impl Guard for EncodingGuard

fn name(&self) -> &str

Get the guard name

fn check(&self, content: &str) -> GuardCheckResult

Check content against this guard

fn action(&self) -> GuardAction

Get the action this guard takes on failure

fn severity_threshold(&self) -> Severity

Get the minimum severity that triggers this guard